Stability of the J-V characteristics of (BEHP-PPV)-co-(MEH-PPV) based light-emitting diodes

0026-2714/$ see front matter 2009 Elsevier Ltd. A doi:10.1016/j.microrel.2009.07.053 * Corresponding author. Address: Sección de Electró Depto. de Ingeniería Electrica, Av. IPN No 2508, Apdo. DF, Mexico. Tel.: +52 55 57473786; fax: +52 55 5747 E-mail addresses: [email protected] (J.C. Sánc [email protected] (M. Estrada). This paper reports main characteristics of copolymer (BEHP-PPV)-co-(MEH-PPV) based PLEDs with PEDOT:PSS as anode and Mg as cathode. Polymeric light-emitting diodes, PLEDs, were prepared by spin-coating of the polymeric layers. Barrier at the anode is around 0.2 eV corresponding to a copolymer HOMO of around 5.3 eV. The energy gap is around 2.3 eV. Photoemission peak is at 547 nm with a refractive index of 1.44. The onset of visible electroluminescence was around J = 100 A/m. The study of the stability of J–V curves showed that for current densities between 620 and 3100 A/m, Joule heating effect associated causes segregation of the PSS from the bulk PEDOT:PSS that increases the anode–copolymer barrier height. For current densities higher than 1500 A/m and for longer operation times, a delamination process in the cathode metal is observed associated to the formation of bubble-like structures that appear as dark spots, leading to final failure of the LED. 2009 Elsevier Ltd. All rights reserved.